Using pure metals and low alloy steel as sample electrodes, the influences of argon flow rate upon the line-intensity of Fe II, Al I and Cu I and the intensity ratio of Al I to Fe I line are investigated.The variation of line intensity and its ratio is thought to be caused by changes in volatility and emissivity of the electrodes.When the argon is introduced into a spark gap in the open air through a glass tube situated so that the gas stream may envelope the spark column, the variation is found to be minimized at an argon flow rate of 1
l/min.However, as the oxygen from the air is not perfectly intercepted by this method, it leads the“diffuse-type”discharge which results in a low spectral intensity and a somewhat time-dependent intensity ratio.
Desirable result is obtained by using a spark chamber made of a quartz tube to avoid oxidation in the spark.When argon gas is introduced into the chamber at a flow rate of 1
l/min., the variation in lines-intensity and intensity ratio is reduced to the minimum.In case of a still atmosphere or a small flow rate such as 0.1
l/min., the erosion rate of iron electrode is low because oxygen and the other gases evolved from the electrodes during sparking are apt to concentrate in the vicinity of the spark gap.
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